Most of the old houses in Luxembourg have either no roof insulation or a very limited old one (max 8 cm).
In order the insulation be effective it should be around 22-24 cm thick, to accommodate it in to the existing roof structure, wooden or metal extension of existing rafters needs to be done.
Another important factor is permeable vapour barrier. Most companies use simple ones, our standard is Intello Plus with variable Sd value that enables a perfect vapour exchange.
Due to the high land price the best way to increase a property value is to increase a number of square meters. The most efficient way of doing it is to change unused attic space into a habitable one.
We have a lot of experience in such works, including space planning, infrastructure, adding bathrooms, simply turning unused space into the part of your home…